Atomizer with liquid spray quenching

Abstract

Method and apparatus for making metallic powder particles wherein a metallic melt is atomized by a rotating disk or other atomizer at an atomizing location in a manner to form molten droplets moving in a direction away from said atomizing location. The atomized droplets pass through a series of thin liquid quenching sheets disposed in succession about the atomizing location with each successive quenching sheet being at an increasing distance from the atomizing location. The atomized droplets are incrementally cooled and optionally passivated as they pass through the series of liquid quenching sheets without distorting the atomized droplets from their generally spherical shape. The atomized, cooled droplets can be received in a chamber having a collection wall disposed outwardly of the series of liquid quenching sheets. A liquid quenchant can be flowed proximate the chamber wall to carry the cooled atomized droplets to a collection chamber where atomized powder particles and the liquid quenchant are separated such that the liquid quenchant can be recycled.

We claim: 
     
       1. Method of making metallic powder particles, comprising: atomizing a metallic melt at an atomizing location in a manner to form molten droplets having generally spherical droplet shape moving in a direction away from said atomizing location, and   passing the atomized droplets through a plurality of thin, generally flat liquid spray quenching sheets disposed in succession about the atomizing location with each successive quenching sheet being at an increasing distance from said atomizing location so that said atomized droplets pass through the liquid spray quenching sheets in succession with said quenching sheets being thin enough in a cross-sectional dimension transverse to said direction that said droplets are incrementally cooled by contact with said quenching sheets as they pass therethrough without substantially distorting the generally spherical droplet shape.   
     
     
       2. The method of claim 1 including the further step of impinging the cooled atomized droplets on an annular liquid quenchant layer flowing in a downward direction generally parallel with an outer atomizing chamber wall outwardly of said plurality of said liquid spray quenching sheets to produce generally spherical particles in a size range from about 50 to about 1000 microns diameter. 
     
     
       3. The method of claim 2 further including entraining the cooled atomized droplets in said liquid quenchant layer and carrying the cooled atomized droplets to a collection chamber. 
     
     
       4. The method of claim 3 further including separating the cooled atomized droplets from the liquid quenchant. 
     
     
       5. The method of claim 1 comprising atomizing said metallic melt at said atomizing location by supplying said metallic melt to a rotating member that centrifugally ejects molten droplets away from said atomizing member. 
     
     
       6. The method of claim 5 comprising supplying said metallic melt to a rotating refractory disk. 
     
     
       7. The method of claim 5 including disposing said plurality of liquid quenching sheets concentrically around an axis of said atomizing location and at successively increasing distances from said atomizing location. 
     
     
       8. The method of claim 1 comprising atomizing said metallic melt in a non-reactive or inert atmosphere or under a relative vacuum as compared to ambient pressure. 
     
     
       9. The method of claim 1 comprising forming each of said liquid quenching sheets by discharging liquid quenchant as a generally flat spray from a plurality of discharge nozzles arranged in a circular pattern such that the sprays collectively form a polygonal cross-section quenching sheet. 
     
     
       10. The method of claim 1 wherein at least one of said liquid quenchant sheets or a reactant therein reacts with said atomized droplets to form a protective coating thereon.